A suicide bomber has killed 23 people at a Shiite procession in the city where Pakistan's army is headquartered, highlighting the country's security challenges a day before it hosts leaders from Egypt, Iran and other developing nations.

The blast ripped a hole in the walls of a Shiite mosque in the city of Rawalpindi, near the capital Islamabad.

A police rescue spokeswoman put the death toll at 23 and said another 62 people were wounded, including eight children.

"The 23 apparently include the bomber because we have pieces of the body that have apparently not been identified," spokeswoan Deeba Shehnaz said.

Hundreds of worshippers, beating their heads and chests, kept marching after the blast. Other explosive devices were later found at the site.

There was no immediate claim of responsibility for the attack which occurred hours after two bomb blasts killed at least three people near a gathering of Shiites in Pakistan's commercial hub and biggest city Karachi.

Pakistan's military, one of the world's biggest, has failed to break the back of a persistent insurgency despite launching several offensives against their strongholds in the north-west near the border with Afghanistan.

Pakistan's standing

Pakistan hosts a summit of eight developing nations on Thursday.

Pakistan, Iran, Egypt, Turkey, Indonesia, Malaysia, Nigeria and Bangladesh are expected to discuss ways of boosting trade and investment at an event which Islamabad hopes will improve its standing. Some presidents have already arrived.

Pakistani interior minister Rehman Malik said the attacks were designed to hurt Pakistan's image and create the impression that its US-backed government is incapable of establishing stability.

"We are trying to build relationships, get investment in Pakistan and these groups are trying to derail the process," he said.

Pakistani authorities are bracing for what could be a bloody weekend, the climax of the Shiite mourning month of Muharram.

Radical Sunni groups have staged high-profile attacks on that occasion in the past.

Thousands of security personnel are expected to be deployed in a bid to avoid attacks.

About 50,000 people are expected to march through the streets of Islamabad on Saturday.

Muharram marks the anniversary of the Battle of Karbala where the grandson of the Prophet Mohammed and his family members were killed.

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